This invention relates to methods and apparatus for recovering spent metals or silver from solution, and particularly to use of ionic exchange chambers for recovering silver as the waste solution flows through a container.
U.S. Pat. Nos. 3,840,217, 3,692,291, 3,630,505 and 4,130,273 relate to apparatus for this type of recovery. These silver recovery units are structured to cause the silver bearing influent to contact an iron exchange metal so that an ionic exchange occurs between the metals with ferric ions replacing the silver ions in the solution and causing precipitation of metallic silver in the form of a sludge. The sludge is then recovered from the container.
Various devices are commercially available to accomplish these results. The various forms of replacement metal used commercially are a mesh screen material, spun steel wool, or iron filings glued to filter material. In the King, Jr., patent, U.S. Pat. No. 4,331,473, the metallic exchange medium comprises specially prepared buoyant elements composed of sponge iron glued or otherwise permanently adhered to expanded polystyrene beads. Although all of these forms of replacement metal are effective to accomplish the intended results, there is a need for lower cost devices in which the entire unit can be discarded after a reasonable period of use, and which does not involve an excessive amount of preparation prior to use.
This invention relates to improvements to the apparatus described above and to solutions to some of the problems raised thereby.